Arthropod-borne viruses (arboviruses) such as chikungunya (CHIKV) and Zika (ZIKV), as well as rodent- and bat-borne viruses such as Lassa fever and probably Ebola, are among the most important causes of emerging infectious diseases, and many circulate enzootically in W. Africa. The mechanisms whereby these and other zoonotic African viruses emerge and spread remain obscure, along with the understanding of their disease burden and varied clinical outcomes. The West African Center for Emerging Infectious Diseases will address these critical gaps through field studies of enzootic transmission, and clinical studies of human exposure and disease outcome. Our surveillance of humans, and wild animals, including bats (probable hosts of filoviruses, coronaviruses and henipaviruses), and mosquitoes/ticks, will likely identify new emerging viral pathogens. Further, the infrastructure and local expertise developed through these projects in Senegal, Sierra Leone and Nigeria, along with biosafety/biosecurity training and improved diagnostics, will also prepare the region for future outbreaks of emerging viral and other infectious diseases. The Center?s aims are to: 1. Study zoonotic arboviruses in Senegal, Sierra Leone and Nigeria, including identification and characterization of critical reservoir and amplification hosts, enzootic and epidemic vectors, temporal patterns of enzootic and epidemic circulation, levels of human exposure, immune responses and disease outcomes. The emphasis will be on the 4 ?urban? (human amplified) arboviruses: CHIKV, DENV, YFV and ZIKV, but other known and possibly unknown viruses will also be studied. Risk maps will be generated. 2. In Sierra Leone and Nigeria, study the circulation among rodent hosts and infections of humans by Lassa virus, including identification of viral determinants of hemorrhagic disease severity and sequelae outcomes, and determination of the mechanisms of strain virulence variation. Risk maps will also be generated. 3. Perform surveillance in bats to identify potential sources of Ebola virus in W. Africa as well as other known or unknown zoonotic pathogens, including coronaviruses and henipaviruses that may be causing human disease, and which may explain the origins of emerging pathogens such as Nipah and MERS coronavirus. 4. Establish biocontainment and biosecurity training programs, advanced yet affordable viral genomics capabilities, and comprehensive diagnostics to support these aims as well as to improve research infrastructure and future outbreak responses in W. Africa. Our results will increase the mechanistic understanding of zoonotic viral maintenance and emergence, etiologies of febrile and hemorrhagic diseases, diverse disease outcomes, and risks for local and international spread. Novel viruses with emergence potential will likely be discovered, and existing collaborations between the Univ. of TX Medical Branch and its partners in Senegal, Sierra Leone, and Nigeria, as well as research infrastructure, will be strengthened to prepare for and respond quickly and effectively to future outbreaks.